Heat exchanger for the transfer of sensible heat and heat of condensation from a gasto a heat-absorbing fluid



3,316,961 AND HEAT 4 Sheets-Sheet 1 -ABSORBING FLUID DORNER ANSFER OF SENSIBLE HEAT GAS TO A HEAT Armin Dorner INVENTOR.

AGENT H IIIHHII llllfllI/rr ON FROM A OF CONDENSATI Filed NOV. 30, 1964 May 2, 1967 HEAT EXCHANGER FOR THE TR May 2, 1967 A. DORNER 3,316,961

HEAT EXCHANGER FOR THE TRANSFER OF SENSIBLE HEAT AND HEAT OF CONDENSATION FROM A GAS TO A HEAT-ABSORBING FLUID Filed Nov. 30. 1964 4 Sheets-Sheet 2 Armin Dorner INVENTOR.

May 2, 1967 DORNER 3,316,961

HEAT EXCHANGER FOR THE TRANSFER OF SENSIBLE HEAT AND HEAT OF CONDENSATION FROM A GAS TO A HEAT-ABSORBING FLUID Filed Nov. 30, 1964 4 Sheets-Sheet :5

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AGENT A. DORNER 3,316,961

AT AND HEAT "ABSORBING FLUID May 2, 1967 HEAT EXCHANGER FOR THE TRANSFER OF SENSIBLE HE OF CONDENSATION FROM A GAS TO A HEAT Filed NOV. 30,

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United States Patent Ofiice 3,316,961 HEAT EXCHANGER FOR THE TRANSFER OF SENSIBLE HEAT AND HEAT F CONDENSA- TION FROM A GAS TO A HEAT-ABSORBING FLUID Armin Dormer, Munich, Germany, assignor to Lmde Aktiengesellschaft, a corporation of Germany Filed Nov. 30, 1964, her. No. 414,908 Claims priority, application Germany, Dec. 2, 1963, G 39,291 9 Claims. (Cl. 165-145) The present invention relates to heat exchangers of the type in which a first fluid, generally at a relatively elevated temperature, transfers its sensible heat and/or heat of condensation to a relatively cool fluid through a heattransmittable wall separating the two fluids.

Heat exchangers of this general type have been provided heretofore with plate-like walls between the compartments, nests of tubes through which one or the other of the fluids is conducted, and fin-like ducts formed by joining plates having channels formed therein.

In the use of such heat exchangers, as for example in rectification systems for the separation of gases by lowtemperature, fractional liquefaction or distillation, it is frequently desirable to employ the transferred heat to vaporize or gasify an at least partially liquid fluid medium adapted to take up the heat. Thus, heat exchangers of this character are employed for the vaporization of the liquid products removed at the base of a rectification tower or at its sump. The vaporization of such liquids requires a heat exchanger whose height or length is relatively small with reference to the longitudinal dimension of the heat-exchanger tubes or the like in order to provide sufiicient space above the liquid for expansion as the gas is formed. For this reason, nested-tnbe heat exchangers generally have a limited tube height only from one to three meters which cannot be exceeded for the reason indicated. The use of relatively short tubes is, however, disadvantageous in nested'tube arrangements since, with a reduced height, in order to obtain a relatively long contact time, the velocity of flow of the gas to be cooled must be proportionately low. This disadvantage is obvious since good transfer of sensible heat requires high flow velocities; less obvious disadvantages include the need for a greater number of tubes in a conventional heat exchanger; the requirement that a number of heat exchangers be provided; and a larger expense for materials, circulating apparatus and the like.

It is a principal object of the present invention to provide a heat exchanger for the purpose described wherein, however, the foregoing disadvantages are obviated.

A further object of the present invention is to provide a heat exchanger suitable for the transfer of both sensible heat and heat of condensation to a heat-absorbing fluid wherein the disadvantages hitherto characterizing the use of relatively short tubes for sensible-heat transfer can be avoided.

These objects and others which will become apparent hereinafter are attained in accordance with the present invention by subdividing a heat exchanger into two sections through which the gas to be cooled is passed in succession and which includes, as the first section, a relatively long heat-transfer path during which sensible heat is transferred to a heat-absorbing fluid; the second section provides a relatively short transport path during which the heat-yielding fluid is able to give up heat of condensation and thus become liquid. It is an essential feature of this invention that the two portions of the heat exchanger path extend between a longitudinally spaced inlet and outlet such that the inlet of the subsequent portion of the path communicates with the outlet of the preceding portion, the two heat-exchanger sections being coaxially nested 3,316,961 Patented May 2, 1967 and having substantially identical axial length. Thus the present invention resides in a heat exchanger Whose first section (provided for the transfer of sensible heat) has a tortuous configuration with respect to the axis, i.e. is in the form of a spiral or helix, while the second section is constituted by substantially linearly extending passages. The helicoidal bundle of tubes in which the sensible heat is transferred has a relatively reduced total flow crosssection so that the high optimal velocity for heat exchange can be attained. The bundle of linearly extending (i.e. parallel to the axis) tubes has a relatively large total flow cross-section and is employed for the transfer of the heat of condensation to the heat-absorbing medium surrounding the two nested sets of tubes.

According to a more specific feature of this invention, the heat exchanger is provided with a cylindrical shell or housing having a vertical axis about which the tubes of the two arrays or bundles are symmetrically disposed. This shell is provided with a pair of axially spaced generally radial ports, the lower of which can be used for the introduction of the heat-receptive medium adapted to surround the tubes. The upper port then constitutes the outlet for the heated fluid. In one arrangement of this system, the ends of the cylindrical shell are closed by a pair of plates extending perpendicularly to the axis of the shell and serving as terminals for the both arrays.

When the coaxially nested arrays include the helicoidal array as the central section, with the axially extending tubes disposed about its periphery, it is: preferred to provide a tubular core about which the inner array can be wound, this core serving advantageously as an axial inlet for the gas to be cooled. Alternatively, the core can be closed while a separate inlet is provided for the hot gases. In either case, it has been found desirable to provide a hood over each of the plates, the hoods defining manifold compartments for the tubes to which the fluid is led in parallel. Furthermore, it is desirable to introduce the hot fluid into the helicoidal tubes from below so that the gas, freed from its excess sensible heat, can pass over, via the upper hood, into the linear tubes whereby the gas travels downwardly while it yields its heat of condensation and is the least partially liquified. The upper hood thus constitutes a communication between the tubes of the two arrays while the lower hood serves as an inlet and an outlet for the gas whose heat is to be transferred. The cooler gas or liquid is separated from the incoming relatively hot gas by an annular partition in the lower hood, this partition subdividing the hood into an outer annular chamber communicating with the outer array and a central chamber communicating with the inner array.

According to still another feature of the present invention, no tubular core is provided and the central part of the cylindrical housing is filled with the axially extending tubes while the array of helicoidal tubes is wound around the axially extending tubes constituted as the central array.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the following example and the accompanying drawing in which:

FIG. 1 is an axially cross-sectional view through a heat exchanger according to the present invention;

FIG. 1A is a cross-sectional view taken along the line IA-IA of FIG. 1;

FIG. 2 is an axial cross-sectional view through another heat exchanger wherein the central array of axial tubes forms a core for the helicoidal array Wound therearound; and

FIG. 3 is an axial cross-sectional view through a heat exchanger similar to that of FIG. 1 but With other fluidsupply means.

opposite ends of the tubes of In FIGS. 1 and 1A there is shown a heat exchanger having a cylindrical shell or housing 1 formed with a pair of axially spaced generally radial fittings 2 and 3 forming an inlet port and an outlet port respectively. It will be understood that a relatively cool heat-absorbing fluid, preferably a liquid to be vaporized or gasified, is introduced via the inlet port 2 to the interior of the housing while at the outlet port 3, the vapors and/ or heated liquid are removed. The shell 1 is provided with a pair of annular flanges 1', 1 adapted to be bolted to the corresponding flanges 15', 9' of the upper and lower hoods 15 and 9 whose function will be described subsequently. A pair of axially spaced plates 4 and 5 extend transversely to the axis of the shell 1 and define the ends of the housing while serving as manifold plates and as terminals for the two arrays of tubes. The plates 4 and 5 are constituted as annular disks and are welded at 4' and 5 to a tubular core 6 closed at its opposite extremities. A first array 7 of tubes is axially wound about the core 6 and terminates at a central zone of the plates 4 and 5, the tubes being wound with several turns, at least, about the core over the axial length thereof, the helicoidal array having a total fluid cross-section substantially less than the flow crosssection of the outer array '8 of tubes extending parallel to the axis and terminating at an outer zone of each plate 4 and 5. The tubes 7 are wound about the core 6 helicoidally and in layers so that their actual length can be several times the effective length of the tubes 8. The inlet for the hot fluid is formed by a flanged fitting 12 opening axially into the hood 9 and communicating with a central compartment 11 therein, defined by the annular partition 10. Compartment 11 registers with the central zone and communicates with the tubes 7 while the annular outer compartment 13 of the hood 9 is in registry with the outer zone and communicates with the tubes 8 for conducting condensate out of the heat exchanger via flange fitting 14. An O-ring 9 is held between the flanges 1" and 9 of the hood 9 and shell 1 and serves as a circumferential seal for the plate 5 thereby preventing escape of fluid from the interior of the housing 1 into the compartment 13. Since the O-ring can be resilient, it can have suflicient elasticity to permit axial expansion of the assembly 48 as a consequence of thermal changes. Alternatively the O-ring can slidably engage the periphery of plate 5.

The upper hood 15 defines with plate 4 a chamber 16 which interconnects the bundles of tubes 7 and 8 so that the gas flows in succession through them as indicated by the arrows. The flanges 1 and 15 hold the plate 4 rigidly in place. The assembly 4-8 is preferably formed by inserting the tubes 7 and 8 in previously drilled bores of the annular disks 4 and 5 after inserting the tubular core 6. Only after the tube 6 has been welded to the plates 4 and 5, the entire assembly is fixed in place. While it may also 'be desired to sweat-solder the tubes 7 and 8 to the disks 4 and 5, it is also possible to press-fit it then so that no additional scaling is required.

The system of FIG. 2 differs from that of FIG. 1 in that the axially extending tubes 108 constitute the central core about which the tubes 107 are helicoidally wound. The housing 101 can thus be identical to that of FIG. 1 and is provided with the inlet 102 and the outlet 103. In this arrangement, however, the lower hood 109 is formed with a pair of inlets 112 about the periphery of this hood, the inlet communicating with an annular compartment 111 which serves as a manifold chamber registering with the outer zone of the tubes 107 and communicating therewith. The partition 110 separates the annular compartment 111 from the central compartment 113 in which the condensate is collected from the linear tubes 108 as the gas introduced at 112 gives up its heat of condensation. An outlet 114 serves to conduct the condensate from the heat exchanger. The plates 104 and 105 are held in place as described with respect to plates 4 and 5 although they are now formed with annular zones at which the tubes 107 of the helical array terminate. Conversely, the central zone of each disk serves as the terminus for the respective end of each tube 108. The upper hood 115 again defines the compartment 116 by means of which the gases stripped of sensible heat are passed from the outer array into the inner array to yield their heat or condensation. In this case, there is no core aside from the tubes 108 and no axially extending tube 6 need be provided.

In the variant of FIG. 3 which is identical to FIG. 1 except that the lower hood 209 is not provided with an inlet since the tube 206 is not closed in this case but extends through the upper hood 215 and its annular compartment 216 to serve as an inlet for the hot gases. The latter pass from tube 206 into the chamber 211 and thence through the central array of helical tubes 207. The partition 210 again defines the outer annular compartment 213 in which the condensate is connected, a fitting 214 being provided to lead the condensate away. The fluid thereby vaporized is introduced at port 202 and is removed at 20 3 as the vapor or a mixture of vapor or liquid. The annular disks 204, 20-5 here serve to hold the tube 206 in place and as terminals for the helicoidal tubes 207 and the linearly extending tubes 208. A releasable connection is provided between the tube 206 and the hood 215 in the form of a stopper-like bushing 217 which is accordion-pleated at 218 for resilient extension upon thermal elongation or shortening of tube 206. A connecting tube 219 is received in the bushing 215 and is flanged to the latter and to tube 206 by bolts 220.

The following example will explain the operation of the invention in greater detail:

Example The heat exchanger is to be used for the vaporization of 20,400 m. /hour (S.T.P.) of propane at a pressure of 14 atm. This quantity of propane is passed through the housing 1, 101, 201. 21,200 mfi/hour (S.T.P.) of propylene at a pressure of 18.5 atm. is cooled from a temperature of 55 C. in the helicoidal array of tubes and is then passed through the linearly extending tubes for condensation at a temperature of 44 C. At the indicated pressure, propane evaporates at 325 C. so that the temperature diiference between the surrounding medium and the temperature within the helical tube bundle is 16.5 C. while the difference between the surrounding medium and the substance in the linearly extending tubes is 115 C. The helically wound array of tubes includes 275 tubes having a nominal size of 25 mm. and a length of 4.07 m. while the 4000 linear tubes have the same nominal size and a length of 1.67 m. The array of helical tubes has a mean heating surface of 81 m? while the array of linear tubes has an effective transfer area of 483 m. The eifective rate of flow (flow velocity) in the bundle of helically wound tubes is substantially higher than the velocity of the linear tubes (i.e., 61.8 m./sec.).

When instead of a helical array of tubes, one operates with a bundle of axially extending tubes, it is necessary to employ more than 10,000 tubes of a nominal size of 25 mm. and a length of 1.67 m. as a consequence of the poorer heat transfer efiiciency and reduced flow velocity. This number is required for parallel flow rather than series flow between two sections. When, however, a series flow is employed, 1650 tubes (approximately) with a transfer area of 200 m? is required to obtain results approaching those of the present invention.

The invention described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the appended claims.

I claim:

1. A heat-exchanger system for the transfer of heat from a relatively warm condensable fluid to a heat-absorbing fluid, comprising housing means forming a heat-exchanger chamber, said housing means being provided with an inlet for supplying said heat-absorbing fluid to said means is a generally cylindrical shell having a chamber, and an outlet for removing said heat-absorbing fluid from said chamber subsequent to its absorption of heat therein; an array of generally helicoidally extending tubes in said chamber in heat-transferring relationship with the heat-absorbing fluid therein; an array of generally linearly extending tubes in heat-transferring relationship with said heat-absorbing fluid in said chamber; said array of generally helicoidally extending tubes and said array of generally linearly extending tubes being coaxially nested; first means for supplying said relatively Warm condensable fluid to said helicoidally extending tubes whereby sensible heat of said condensable fluid is transferred to said heat-absorbing fluid; second means for passing the condensable fluid emerging from said helicoidally extending tubes to said linearly extending tubes whereby heat of condensation of said condensable fluid is transferred to said heat-absorbing fluid; and third means for discharging fluid from said linearly extending tubes, said helicoidally extending tubes being of substantially greater length than said linearly extending tubes in heat-transferring relationship with said heat-absorbing fluid, and said array of helicoidally extending tubes having a total flow cross-section substantially less than the total flow cross-section of said linearly extending tubes.

'2. A system as defined in claim 1 wherein said housing substantially vertical axis, said system further comprising a pair of axially spaced disks extending generally transversely to said axis and defining said chamber with said shell, said tubes terminating at their opposite extremities at said disks and opening axially outwardly of said chamber, said second means forming a compartment at an upper axial end of said shell above the upper disk communicating with all of said tubes, said arrays being coaxially nested in said chamber.

3. A system as defined in claim 2 wherein said linearly extending tubes are parallel to said axis and said array of helicoidally extending tubes surrounds said axis, said second means including a hood axially above said chamber and enclosing the upper one of said disks While defining therewith said compartment, each of said arrays terminating in a respective zone at the lower one of said disks, said zones being axially symmetrical, said first and third means including a further hood below said chamber and enclosing the lower one of said disks while defining therewith a pair of further compartment each communicating with the tubes of a respective array and registering with the corresponding one of said zones.

4. A system as defined in claim 3 wherein said further hood is provided with an annular partition intermediate said zones and separating said compartments of each array, said first means including an inlet duct communicating with the compartment of said further hood communicating with said helicoidal tubes, said third means including an outlet duct communicating with the compartment of said further hood communicating with said linearly extending tubes.

5. A system as defined in claim 4 wherein said array of linearly extending tubes is disposed centrally in said chamber and said array of helicoidally extending tubes is wound about the array of linearly extending tubes.

6. A system as defined in claim 4 wherein said disks are interconnected by a axially extending conduit rigid with said disks, said array of helicoidally extending tubes surrounding said conduit, said linearly extending tubes being disposed outwardly of said helicoidally extending tubes.

7. A system as defined in claim 6 wherein said conduit is closed at its opposite ends.

8. A system as defined in claim 6 wherein said conduit forms said inlet duct and extends into the compartment of said further hood communicating with said helicoidal tubes.

9. A system as defined in claim 8 wherein said conduit extends upwardly beyond said upper disk and through the hood thereabove, said system further comprising releasable means sealingly and detachably connecting said conduit with the hood above said upper disk.

References Cited by the Examiner UNITED STATES PATENTS 1,073,746 9/1913 Dwyer 165- 146 1,091,369 3/1914 Mejani 165163 1,343,669 6/1920 Funderburk 165-163 3,158,010 11/1964 Kuerston l145 X FOREIGN PATENTS 267,005 11/1913 Germany.

ROBERT A. OLEARY, Primary Examiner. A. DAVIS, Assistant Examiner. 

1. A HEAT-EXCHANGER SYSTEM FOR THE TRANSFER OF HEAT FROM A RELATIVELY WARM CONDENSABLE FLUID TO A HEAT-ABSORBING FLUID, COMPRISING HOUSING MEANS FORMING A HEAT-EXCHANGER CHAMBER, SAID HOUSING MEANS BEING PROVIDED WITH AN INLET FOR SUPPLYING SAID HEAT-ABSORBING FLUID TO SAID CHAMBER, AND AN OUTLET FOR REMOVING SAID HEAT-ABSORBING FLUID FROM SAID CHAMBER SUBSEQUENT TO ITS ABSORPTION OF HEAT THEREIN; AN ARRAY OF GENERALLY HELICOIDALLY EXTENDING TUBES IN SAID CHAMBER IN HEAT-TRANSFERRING RELATIONSHIP WITH THE HEAT-ABSORBING FLUID THEREIN; AN ARRAY OF GENERALLY LINEARLY EXTENDING TUBES IN HEAT-TRANSFERRING RELATIONSHIP WITH SAID HEAT-ABSORBING FLUID IN SAID CHAMBER; SAID ARRAY OF GENERALLY HELICODIALLY EXTENDING TUBES BEING SAID ARRAY OFF GENERALLY LINEARLY EXTENDING TUBES BEING COAXIALLY NESTED; FIRST MEANS FOR SUPPLYING SAID RELATIVELY WARM CONDENSABLE FLUID TO SAID HELICOIDALLY EXTENDING TUBES WHEREBY SENSIBLE HEAT OF SAID CONDENSABLE FLUID IS TRANSFERRED TO SAID HEAT-ABSORBING FLUID; SECOND MEANS FOR PASSING THE CONDENSABLE FLUID EMERGING FROM SAID HELICODIALLY EXTENDING TUBES TO SAID LINEARLY EXTENDING TUBES WHEREBY HEAT OF CONDENSATION OF SAID CONDENSABLE FLUID IS TRANSFERRED TO SAID HEAT-ABSORBING FLUID; AND THIRD MEANS FOR DISCHARGING FLUID FROM SAID LINEARLY EXTENDING TUBES, SAID HELICOIDALLY EXTENDING TUBES BEING OF SUBSTANTIALLY GREATER LENGTH THAN SAID LINEARLY EXTENDING TUBES IN HEAT-TRANSFERRING RELATIONSHIP WITH SAID HEAT-ABSORBING FLUID, AND SAID ARRAY OF HELICOIDALLY EXTENDING TUBES HAVING A TOTAL FLOW CROSS-SECTION SUBSTANTIALLY LESS THAN THE TOTAL FLOW CROSS-SECTION OF SAID LINEARLY EXTENDING TUBES. 